An arrhythmia is a disturbance in the normal rate, rhythm or conduction of the heartbeat. An atrial arrhythmia originates in the atria. Atrial tachycardia (AT), one form of atrial arrhythmia, is a condition in which the atria contract at a high rate, e.g., 100 or more beats per minute. Atrial fibrillation (AF), another form of atrial arrhythmia, is characterized by a chaotic and turbulent activation of atrial wall tissue. AT can lead to AF, which in turn can be life threatening.
Treatment for tachycardia may include anti-tachycardia pacing (ATP) or cardioversion, in which a train of high rate pulses or one or more high energy pulses is delivered to the heart in an attempt to restore a more normal rhythm. ATP is typically effective in converting stable atrial tachycardias to normal rhythm, and is often delivered via an implanted device. In many cases, a sequence of increasingly aggressive ATP therapies are applied until an episode of AT is terminated. Some implanted devices can be configured to discontinue ATP and immediately apply cardioversion in the event the AT degrades into AF.